$$group

Groups an array of elements into a map of key:array

Usage

{
  "$$group": [ /* values */ ],
  "by": /* Transformer */,
  "order":  /* direction of ordering */,
  "type": /* type of values (to order by) */,
  "then": [ /* secondary grouping */
    {
      "by": /* Transformer */,
      "order":  /* direction of ordering */,
      "type": /* type of values (to order by) */,
    },
    ...
  ]
}

"$$group:{input}"

Returns

object (Map<String, Array>)

Arguments

Argument	Type	Values	Required / Default Value	Description
Primary	array		Yes	Array of elements
by	Transformer	Input is ##current (current element)	Yes	A transformer to extract a property to group by
order	Enum	ASC/DESC	ASC	Direction of ordering (ascending / descending)
type	Enum	auto/string/number/boolean	auto	Type of values to expect when ordering the input array
then	array	Array of items containing by,order & type		An array of subsequent grouping.

Examples

Input

Definition

Output

[
  { "o": 1, "p": 11, "w":"aaa"},
  { "o": 1, "p": 13, "w":"bbb"},
  { "o": 1, "p": 11, "w":"ccc"},
  { "o": 2, "p": 11, "w":"ddd"},
  { "o": 2, "p": 13, "w":"eee"},
  { "o": 3, "p": 12, "w":"fff"},
  { "o": 1, "p": 9, "w":"zzz"}
]

{
   "$$group": "$",
   "by": "##current.o",
   "then": [
     {
       "by": { 
         "$$join": [ 
           "p_", 
           "##current.p" 
         ] 
       },
       "order": "DESC"
     }
   ]
 }

{
  "1": {
    "p_9": [
      {
        "o": 1,
        "p": 9,
        "w": "zzz"
      }
    ],
    "p_13": [
      {
        "o": 1,
        "p": 13,
        "w": "bbb"
      }
    ],
    "p_11": [
      {
        "o": 1,
        "p": 11,
        "w": "aaa"
      },
      {
        "o": 1,
        "p": 11,
        "w": "ccc"
      }
    ]
  },
  "2": {
    "p_13": [
      {
        "o": 2,
        "p": 13,
        "w": "eee"
      }
    ],
    "p_11": [
      {
        "o": 2,
        "p": 11,
        "w": "ddd"
      }
    ]
  },
  "3": {
    "p_12": [
      {
        "o": 3,
        "p": 12,
        "w": "fff"
      }
    ]
  }
}

[
  ["a", 1],
  ["b", true],
  ["c", "C"],
  ["c", "D"]
]

"$$group:$"

{
  "a": [1], 
  "b": [true], 
  "c": ["C", "D"]
}

[
  ["a", 0, 1],
  ["a", 1, true],
  ["a", 2, "C"],
  ["b", 1, 6]
]

"$$group:$"

{
  "a": {
    "0": [1],
    "1": [true],
    "2": ["C"]
  },
  "b": {
    "1": [6]
  }
}